Landau Free Energy of small clusters beyond mean field approach

The Landau Free Energy determines the landscape of order parameter fluctuations that occur in a physical system at thermal equilibrium and, in particular, characterizes the critical phenomena. We propose a semi-analytical approach based on the Fluctuating Local Field method, which allows to estimate Landau Free Energy for small clusters with discrete (Ising model) and continuous (Heisenberg model) order parameter.